In response, Google’s Danny Sullivan confirmed this is a limited experiment which happens to be “overtriggering” at the moment.

Sullivan also mentions it wasn’t Google’s intention for ads to be displayed on that screen.

“This is a narrow experiment focused on times when our systems detect there is little relevant content available on the web for the given query. It appears to be overtriggering. We will investigate and adjust, including ensuring ads don’t show by default. That wasn’t intended.”

It would be interesting to see a running list of queries that trigger this experiment. I can’t recall many times where I’ve searched for something and didn’t see at least one relevant result.

If you run into this experiment, perhaps you find a way to take advantage by creating relevant content for queries where there isn’t any.